Noel H. Turner

Extracting Auger lineshapes from experimental data

Abstract A method is presented for extracting Auger lineshapes from an experimental, derivative Auger electron spectrum. The method involves removing the background after numerically integrating the derivative spectrum. This procedure is contrasted with the “dynamic background subtraction” method and similar methods which remove the background before integration. A treatment of electron energy loss is included. A functional form for the total electron emission for the Li salts of SO 4 3− and PO 4 3− is presented and compared to electron-loss data. Electron escape depth and spectrometer response corrections to the observed Auger signal are also considered. The S and P LVV Auger lineshapes are presented for the third row oxyanions, SO 4 2− PO 4 3− .

An interpretation of the Auger LVV transitions from oxides of third-row elements

Abstract The principal features in the LVV Auger spectra from the oxides of third-row elements are semi-empirically derived for the XO 4 n − species of Si, PS and Cl, and the XO 6 n − species of Mg and Al. Electron molecular orbital energies are derived from X-ray photoelectron and X-ray emission spectra; the central atom 3 p electron density of states is taken from the K β X-ray emission. Two principal peaks, separated by ca. 14 eV, are predicted for the central atom LVV Auger spectra and are experimentally confirmed for the XO 4 n − species. Similar features are observed in published spectra for oxides of Mg and Al. These peaks correspond to central atom 3 p electrons in orbitals whose energy is dominated by the atomic oxygen 2 s and 2 p electron levels. An examination of the total LVV line-shape shows that a self-convolution of the K β spectra does not reproduce the more subtle features, which are probably a result of the contributions of other electron orbitals and final-state effects. The possibility of using the LVV Auger spectra to discriminate between various oxide stoichiometries, i.e. sulfate, sulfite, etc., and between various ligand species, i.e. carbide, nitride, oxide, fluoride, is discussed.

20 nm linewidth platinum pattern fabrication using conformal effusive‐source molecular precursor deposition and sidewall lithography

In a manner suitable for large‐scale processing, vertical platinum structures having thicknesses (linewidths) down to 20 nm, heights up to 700 nm, an aspect ratio up to 13, and different geometric shapes have been fabricated on top of a silicon dioxide substrate by Pt deposition from the thermal decomposition of a platinum precursor molecule under gas phase collisionless conditions followed by ion‐assisted etching. Scanning electron microscopy analysis shows that the structures have very small grains, high uniformity, and very sharp contours, demonstrating a high degree of conformal deposition. Scanning Auger microscopy reveals platinum only on the structures. X‐ray diffraction and x‐ray photoelectron spectroscopy analysis of the as‐deposited platinum film show that the platinum film is polycrystalline and has no detectable impurity. Scotch tape test shows good bonding of the film. Mass spectrometric measurements suggest that substantial amounts of stable precursor fragments from partial decomposition of ...

CALCULATED AND MEASURED AUGER LINESHAPES IN SiO2

ABSTRACT The Si L1L23V, Si L23VV and 0 KVV Auger lineshapes in SiO2 have been measured and calculated. The Auger transition energies and linewidths are estimated from one electron calculations; the intensities are estimated from electron densities local to the core hole multiplied times atomic Auger matrix elements. The calculated energies and measured values agree within the uncertainties. The calculated intensities are in general agreement with experiment, however there is some disagreement with Kβ X-ray emission observations of the local electron density on silicon. The calculated linewidth is too small when there are two localized holes in the final state.

Influences exerted by metal deactivator on the thermal stability of aviation fuel in the presence of copper

ABSTRACT It has been shown that metal deactivator additives (MDA) exert a strong stabilizing effect on fuels when tested in the Jet Fuel Thermal Oxidation Tester (JFTOT). At low concentrations, MDA was found to be very effective in the JFTOT in reducing insoluble reaction products but had no significant effect on fuel oxidation. In the presence of dissolved copper, MDA acted to reduce tube deposition over regions of the tube at which temperatures were higher than 250°C. The deposits formed in the presence of copper at lower temperatures, which were not reduced by the MDA, were found to contain a high concentration of copper. MDA also partially counteracted the catalytic effects of dissolved copper on fuel autoxidation.

Low-temperature deposition of films from tetrakis(dimethylamido)titanium and ammonia

Abstract We report the chemical vapor deposition (CVD) and characterization of thin films grown from the reaction of tetrakis(dimethylamido)titanium (Ti(NMe2)4, TDMAT) with NH3 at 423 K. These films, deposited on a variety of substrates, are amorphous except for a small number of embedded nanocrystallites. The films exhibit peeling at thicknesses greater than ca. 200 nm on all substrates and show no visible evidence of etching after exposure to concentrated hydrochloric or nitric acid for 5 min. X-ray photoelectron spectroscopy (XPS) results yield a N/Ti ratio of 0.89 after normalizing the data to that of a TiN standard. The O/Ti ratio varies from 0.26 to 0.66, and the C content is less than 1 at.%. Transmission Fourier transform infrared (FTIR) spectroscopy of films deposited on Si gives spectra consistent with the presence of N–H bonds.

Selective area platinum silicide film deposition using a molecular precursor chemical beam source

Abstract Selective area deposition of platinum suicide on exposed silicon areas of n-type, Si(100) substrates patterned with a polyimide resist has been demonstrated by using the thermal decomposition of the molecular precursor, Pt(PF3)4, under chemical beam conditions. Selectivity was studied as a function of precursor partial pressure, substrate temperature and duration of deposition. Selectivity was most easily obtained at a precursor partial pressure of 1.33 × 10−4 Pa, substrate temperature of 250 °C and deposition times ranging from 18 to 30 min. Atomic force microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy analyses of selectively deposited films strongly suggested the complete interdiffusion of Si and Pt. Speculations on possible mechanisms for selectivity are discussed.

Accurate determination of Auger line shape binding energies

Abstract A quantitative comparison between an experimental and a theoretical description of any Auger spectrum requires a common energy reference point such as the Fermi level. With non-conductors this is problematic, because the Fermi level is not well defined and charging may shift the Fermi level. A common approach used to overcome this problem employs spectra containing the Auger peak, core, and valence band (VB) photoemission peaks. It is then necessary only to locate a common reference point in the Auger and VB spectra relative to the core level peak. We have developed a procedure in which a comparison is made between model theoretical and experimental spectra so that a large energy range (about 20 eV) of each spectrum can be utilized to locate the common reference points. We have found that this method enables accurate reference points to be determined even with severe sample charging. The method is precise enough to observe a differential charging effect in the polyethylene (PE) spectra. Although much smaller than that previously reported, a breakdown in the Cini-Sawatzky expression as modified for covalent systems still is suggested for PE. This breakdown can now be attributed to the limited one-dimensional delocalization required in long chain polymers.

Introduction of Water Vapor into Vacuum Systems and the Adsorption by the Walls

A technique is described whereby precise amounts of water vapor can be introduced into evacuated glass–Kovar stainless-steel systems. The adsorption of water vapor by the walls of a typical vacuum system maintained at 26.8°C is reported in the range 0.03–0.20 relative pressure. A continuous dynamic behavior was observed over time intervals up to 4000 min, where time zero corresponds to the initial contact of the walls with the water vapor. At a constant contact time, the pressure dependence of each isochrone followed a conventional Type II physical adsorption isotherm and a linear B.E.T. plot was observed in the range 0.04 and 0.18 relative pressures. It is quite feasible to follow the adsorption of water vapor volumetrically on a variety of solids at all pressures above an absolute pressure of 0.1 Torr due to the good reproducibility of the wall adsorption, provided the isochronal nature of the adsorption process is recognized.

A comparison of X-ray photoelectron spectroscopy and Auger electron spectroscopy depth profiles for magnesium implants

Abstract The analysis of depth profiles when magnesium is present gives rise to several analytical problems with either X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES). With both techniques the relative sensitivity is low for the main transition usually employed, i.e., the 2s photoemission line in XPS and the KLL transition in electron-excited AES. With XPS, the Al X-ray-excited Mg KLL peak has a relative intensity that is greater than the 2s transition, but not with Mg radiation. The peak-to-peak height of the electron-excited AES peak can vary with the chemical state of Mg. Also, in some instances overlapping peaks can cause problems. In this study Mg was implanted into metal foils at various levels. Depth profiles were obtained with both XPS and AES, and the instrument-based quantitative analysis computer routines were used with slight modifications. It was found that each technique had its own set of advantages, and both approaches gave roughly comparable profiles. The estimated maximum amounts were below those anticipated from the implant conditions. As expected with XPS, chemical effects could easily be determined. However, a relative sensitivity factor was needed to use the X-ray-excited KLL Auger transition. With AES certain low-level contaminants were more easily detected and monitored. Overall, the XPS profiles appeared to offer better results in most respects for these systems. Other factors, e.g., time of analysis, data treatment methods, detection limits, etc., will be discussed also.